Present broadcast television video signals in the United States are analog signals generated according to the National Television Systems Committee (NTSC) standard. Non-U.S. countries have similar standards such as the Phase Alteration Line (PAL) and Systeme Electronique Color Avec Memoire (SECAM) standards. In the future, these analog television signals, and television signals generated according to newly proposed standards for compressed digital video, e.g., using 16 or 256 level quadrature amplitude modulation (QAM) as well as vestigial sideband (VSB) and offset QAM (OQAM), will be broadcast in the United States, and may be transmitted along with NTSC signals from a single transmitting facility. Ideally, television receivers in the future should be able to receive video signals in multiple modulation formats.
Current proposals for such television receivers envision combining a known analog television signal receiver with a separate known digital television signal receiver. One such receiver is disclosed in U.S. Pat. No. 5,418,815 issued May 23, 1995. This is, effectively, two television receivers combined within a single enclosure. However, there are many signal processing elements which are common to the receiving circuitry for both forms of television signals. This means that such receivers will have circuit elements which are duplicated in the two receiver sections. This leads to increased costs and decreased reliability due to an increased number of components.
Therefore, there is a need in the art for a television receiver that receives both analog and digital television. Such a receiver should have only a single instance of components common to both types of receivers.